In contrast to the wealth of information relating to genes regulating floral meristem and floral organ identity, only limited data are available concerning genes that are involved in determining and regulating the identity and development of an ovule. We have recently isolated the floral binding protein 11 (FBP11) MADS box gene from petunia and found that it is expressed exclusively in ovule primordia and subsequently in the ovules, suggesting a role for this gene in ovule formation. To test this hypothesis, we constructed a recombinant gene in which the full-size FBP11 cDNA was placed under the control of a strong cauliflower mosaic virus 35S promoter. Transgenic petunia plants expressing this chimeric gene have ovulelike structures on the adaxial side of the sepals and the abaxial side of the petals. Detailed morphological studies showed that these ovulelike structures are true ovules. RNA gel blot analysis was performed to investigate ectopic FBP11 expression in relation to the expression of the closely related FBP7 gene and the putative petunia class C-type homeotic genes FBP6 and pMADS3. Our results indicate that FBP11 represents an ovule identity gene. A new model describing the mode of action of FBP11 as an additional class D MADS box gene is presented.

We isolated and characterized two ovule-specific MADS box cDNAs from petunia, designated floral binding protein (fbp) genes 7 and 11. The putative protein products of these genes have approximately 90% of their overall amino acid sequence in common. In situ RNA hybridization experiments revealed that both genes are expressed in the center of the developing gynoecium before ovule primordia are visible. At later developmental stages, hybridization signals were observed only in the ovules, suggesting that these genes are involved in ovule formation. To test this hypothesis, we raised transgenic petunia plants in which both fbp7 and fbp11 expression was inhibited by cosuppression. In the ovary of these transformants, spaghetti-shaped structures developed in positions normally occupied by ovules. These abnormal structures morphologically and functionally resemble style and stigma tissues. Our results show that these MADS box genes belong to a new class of MADS box genes involved in proper ovule development in petunia.

We isolated and characterized two ovule-specific MADS box cDNAs from petunia, designated floral binding protein (fbp) genes 7 and 11. The putative protein products of these genes have -90% of their overall amino acid sequence in common. In situ RNA hybridization experiments revealed that both genes are expressed in the center of the developing gynoecium before ovule primordia are visible. At later developmental stages, hybridization signals were observed only in the ovules, suggesting that these genes are involved in ovule formation. To test this hypothesis, we raised transgenic petunia plants in which both fbp7 and fbp77 expression was inhibited by cosuppression. In the ovary of these transformants, spaghetti-shaped structures developed in positions normally occupied by ovules. These abnormal structures morphologically and functionally resemble style and stigma tissues. Our results show that these MADS box genes belong to a new class of MADS box genes involved in proper ovule development in petunia.

Temperature controls the developmental fate of isolated Brassica napus microspores in vitro. Culture at 32.5°C leads to sporophytic development and the formation of embryos. Here we show that culture at 17.5°C leads to gametophytic development, and the formation of pollen-like structures at high frequencies (up to 80% after 7 days in culture). Early stages of both developmental pathways are observed in culture at 25.0°C, and embryos are produced at low frequencies (0.7%) at that temperature. Culturing B. napus microspores at 32.5°C versus 17.5°C brings the switch from gametophytic to sporophytic development under simple experimental control and provides a convenient tool for investigating the cellular and molecular mechanisms controlling this developmental switch.

In contrast to the wealth of information relating to genes regulating floral meristem and floral organ identity, only limited data are available concerning genes that are involved in determining and regulating the identity and development of an ovule. We have recently isolated the floral binding protein 11 (FBP11) MADS box gene from petunia and found that it is expressed exclusively in ovule primordia and subsequently in the ovules, suggesting a role for this gene in ovule formation. To test this hypothesis, we constructed a recombinant gene in which the full-size FBP11 cDNA was placed under the control of a strong cauliflower mosaic virus 35S promoter. Transgenic petunia plants expressing this chimeric gene have ovulelike structures on the adaxial side of the sepals and the abaxial side of the petals. Detailed morphological studies showed that these ovulelike structures are true ovules. RNA gel blot analysis was performed to investigate ectopic FBP11 expression in relation to the expression of the closely related FBP7 gene and the putative petunia class C-type homeotic genes FBP6 and pMADS3. Our results indicate that FBP11 represents an ovule identity gene. A new model describing the mode of action of FBP11 as an additional class D MADS box gene is presented.